The Monster's Web Voyage to the Bottom of the Sea : Season 2 Episode 23

Captain Gantt, an ego-maniacal scientist, is in a nuclear sub testing a powerful new fuel. Due to his bungling, the sub crashes into a giant web and is attacked by a monstrous sea spider. The Seaview investigates and rushes to retrieve the remaining fuel canisters before the enormous underwater pressure collapses the test sub and detonates the fuel - an explosion which would kill millions!